In a recent electric or electronic equipment (electric or electronic device) (also referred to as electrical equipment), in order to prevent deterioration (inverter surge deterioration) caused by a surge voltage generated by switching of inverter elements, such an insulated wire (wire) that can withstand a surge voltage having several hundred volts has been required in several cases (see Patent Literature 1).
Further, advance of the electrical equipment represented by motors or transformers, has been progressed resulting in size reduction and improved performance. Thus, it becomes usual in many cases that insulated wires are used in such a way that the insulated wires are processed by winding (also referred to as coil processing or bending) to winding the resultant wires (coils) and they are pushed into a quite small space to pack. Specifically, it is no exaggeration to say that the performance of a rotating electric machine, such as a motor, is determined by how many coils produced by coil processing the insulated wires into a coil shape can be held in a stator slot. As a result, improvement of the ratio of the sectional area of conductors to the sectional area of the stator slot (i.e. space factor) has been required to be highly increased. For the reasons discussed above, it has been lately attempted to use a rectangular wire in which the conductor has a cross-sectional shape similar to a quadrilateral (square or rectangle), as a means for increasing the space factor.
The resin to be used in the insulation layer in the insulated wire is ordinarily applied in one kind. However, proposals have recently been made on use of a mixed resin prepared by mixing two kinds of resins.
For example, in order to compensate a disadvantage of poor chemical resistance to readily cause cracks, in a polyethersulfone resin having excellent thermal softening resistance and flexibility, Patent Literature 2 proposes simultaneous use of 10 to 50 mass % of polyphenylenesulfide resin or polyetheretherketone resin. Moreover, in order to achieve heat resistance and high partial discharge inception voltage (PDIV), Patent Literature 3 proposes use of a resin composition having a phase separation structure in which a polyetheretherketone resin is applied as a continuous phase and in which a resin having relative permittivity of 2.6 or less is applied as a dispersed phase. Further, in order to improve insulation property by using a resin having low relative permittivity, Patent Literature 4 proposes mixing of 5 to 50 mass % of fluorocarbon resin formed of a copolymer of perfluoroethylene and perfluorinated alkoxyethylene with an aromatic polyetherketone resin.